Strobe flash apparatus

ABSTRACT

Disclosed herein is a strobe flash apparatus with a modular construction in which the gas-filled flash tube and the circuit components are mounted on a printed circuit board to form a circuit module. The circuit module is mounted in a tubular housing with the camera sync-plug interfitting in a through aperture in the housing wall to anchor the circuit module against axial and angular displacement. The flash tube plugs into a socket at one end of the module and is located within a transparent protective cover to afford 360* light emanation. The circuit includes a light sensitive silicon controlled rectifier located in registry with a window in the housing to afford use of the flash as a light triggered slave unit. An axially shiftable sleeve on the housing is positionable over the window when the flash is triggered with the camera shutter contacts. A neon ready light is located in the transparent cover adjacent the flash tube and blinks or pulsates to indicate that the power pack has recycled and is ready for firing. A high resistance bridge minimizes idling drain of the battery in the power supply, and a high resistance and low current in the semi-conductor isolated trigger circuit minimizes burn of shutter contacts.

22 Filed:

[ 1 July 4,1972

[54] STROBE FLASH APPARATUS Robert M. Hogue, 4425 W. Dunwood Road, Brown Deer, Wis. 53223 March 6, 1970 21 Appl.No.: 17,234

[72] Inventor:

52- use! ..3l5/l49,315/241P,250/239 5n lnt.Cl. ..H05b37/02 53 Field of Search ..240/1.3,20;95/11.5;250/229,

250/237, 239; 317/99, 101 DH, 120; 315/76, 129, 134,135,149,l51153,156, 200, 201, 203, 204, 208, 241 R, 241 P, 241 S Primary Examiner-Roy Lake Assistant Examiner-J. Dahl Lawrence Attorney-Wheeler, House & Wheeler [57] ABSTRACT Disclosed herein is a strobe flash apparatus with a modular construction in which the gas-filled flash tube and the circuit components are mounted on a printed circuit board to form a circuit module. The circuit module is mounted in a tubular housing with the camera sync-plug interfitting in a through aperture in the housing wall to anchor the circuit module against axial and angular displacement. The flash tube plugs into a socket at one end of the module and is located within a transparent protective cover to afford 360 light emanation. The circuit includes a light sensitive silicon controlled rectifier located in registry with a window in the housing to afford use of the flash as a light triggered slave unit. An axially shiftable sleeve on the housing is positionable over the window when the flash is triggered with the camera shutter contacts. A neon ready light is located in the transparent cover adjacent the flash tube and blinks or pulsates to indicate that the power pack has recycled and is ready for firing. A high resistance bridge minimizes idling drain of the battery in the power supply, and a high resistance and low current in the semi-conductor isolated trigger circuit minimizes burn of shutter contacts.

17 Claims, 5 Drawing Figures PAIENTE-nJUL 41972 I 3,675,073

v SHEET 2 0F 2 I39 Kw/7 IIIIIIIIIII INVENTOR. f 9 5 ROBERT M. #00115 ATTORNEYS STROBE FLASH APPARATUS BACKGROUND OF THE INVENTION The invention relates to strobe flash apparatus utilizing a gas-filled flash tube and a capacitor discharge triggering circuit. More particularly the invention relates to flash apparatus adapted for use in reflectorless flash photography and compatible for use with conventional capacitor-type power supplies.

SUMMARY OF INVENTION The invention provides a gas-filled flash tube and circuit module or assembly which is axially inserted in a tubular nonconductive housing. The flash tube is carried by a rigid disc or wafer provided with pins which are receivable in a socket mounted on one end of a circuit board forming part of the circuit module. A neon ready light is resiliently supported on the tube socket in adjacent relation to the flash tube by a heat shrinkable tube which encapsulates the neon bulb electrodes and the lower end of the neon bulb. The neon bulb projects through an aperture in the wafer to afl'ord axial withdrawal of the wafer over the neon bulb assembly. The neon light and aperture also serve as a keying arrangement to facilitate location of the wafer pins in the appropriate socket apertures.

The flash tube is enclosed by a transparent protective tubular cover which frictionally interfits in the upper end of the housing to afford easy removal of the cover for replacement of the flash tube without removal of the circuit board or neon signal light. The lower edge of the cover clamps against the wafer to hold the wafer firmly against the tube socket and thus prevent accidental displacement of the flash tubeand disconnection of the flash tube from the circuit. The small clearance between the wafer and the inside diameter of the tubular housing permits axial withdrawal of the flash tube from the upper end of the housing, but prevents translatory displacement of the circuit board when connecting and disconnecting the power supply cord and camera shutter synchronization cord.

The circuit board assembly is positively located in the housing by the camera synchronization input jack or plug, which is fixedly secured to the circuit board. When the circuit board is assembled in the housing the plug registers with and is located withinan aperture in the housing. The resilience of the circuit board allows the plug to slide on the inside surface of the housing and snap into the aperture. The plug is dislocated from the aperture when disassembling the circuit board by inward external pressure.

The use of the camera sync plug to positively locate the circuit board in the housing in a fixed relationship relative to the housing also insures precise location of a light activated semiconductor switch in a window in the housing to obtain the maximum angle of light acceptance.

Further rigidity for the circuit board is provided by a metal end cap which has a portion which extends into the lower end of the housing. The end cap is provided with a radial slot extending along a diameter line of the inner surface of the cap. The lower end of the circuit board is received in the slot. When the cap is assembled in the housing the slot in the cap extends at right angles or transversely to the direction of thrust on the input plugs when the cords are connected.

The light activated semi-conductor switch permits the flash apparatus to be used for either slave operation using a light trigger, or operation using the camera shutter contacts. An axially shiftable sleeve in frictional engagement with the outside diameter of the tubular housing is positioned over the window when the camera shutter contacts are employed to tire the flash tube to prevent premature ignition by transient light.

The light activated semi-conductor switch is part of a capacitor discharge trigger circuit which utilizes a high resistance bridge to provide a predetermined charge on the trigger storage capacitor. The ratio of the resistors in the bridge insures stability of the semi-conductor switch against intermittent pre-ignition. The high resistance of the bridge also minimizes idling drain of the battery in a battery power supply. A high resistance in series with the camera shutter contacts and gate to anode circuit isolation provided by a semi-conductor switch minimizes shutter burn. The neon ready light is connected in the circuit to form a relaxation oscillator with the neon tube blinking at apparoximately one flash a second to indicate attainment of the predetermined firing charge on the storage capacitor in the power supply.

It is an object of the invention to provide flash apparatus with a tubular housing having a window for exposing a light sensitive semi-conductor switch and in which the window is selectively opened and closed by an axially shiftable sleeve which frictionally engages the housing.

It is a further object of the invention to provide flash apparatus with a tubular housing and in which a circuit module is receivable in one end of the housing and a flash tube assembly is receivable in the other end of the housing and connectable to a tube socket fixed to one end of the circuit module.

It is a further object of the invention to provide flash apparatus in which the flash tube is detachably connectable to a socket forming a part of a circuit module which is receivable within a tubular housing and which supports a ready light, a light sensitive semi-conductor switch and the input plugs.

It is an additional object of the invention to provide a flash circuit which utilizes a high resistance bridge in the trigger circuit to minimize idling current drain and afford stability to a light sensitive semi-conductor switch.

Further objects and advantages of the present invention will become apparent from the following disclosure.

THE DRAWINGS FIG. 1 is a perspective view of flash apparatus in accordance with the invention.

FIG. 2 is an enlarged side elevational view in fragmentary section of the flash apparatus shown in FIG. 1.

FIG. 3 is an enlarged perspective view of the flash tube and circuit module.

FIG. 4 is an enlarged perspective view of the rear of the circuit module shown in FIG. 3.

FIG. 5 is a schematic drawing of the electrical circuit.

DESCRIPTION OF THE DRAWINGS In the drawings, FIG. 1 discloses flash apparatus which is generally designated 10 and which includes a tubular thin wall housing 12 desirably fabricated from an insulating material, such as pressed fiber. The housing 12 has a hollow interior 14 which axially receives a unitary circuit assembly or circuit module 16 (FIG. 3), hereinafter described in detail. The housing includes a window 18 to expose a light sensitive semi-conductor switch 20 (FIG. 2) on the circuit module 16.

In accordance with the invention, semi-rigid means are provided on the outside surface 22 of the housing and freely slidable on the housing for selectively opening and closing the window. In the disclosed construction, the means for selectively opening and closing the window 18 comprises an axially shiftable sleeve 24 in frictional engagement with the outer surface 22 of the housing 12. The sleeve can be fomied from a short length of housing material which is cut or slit axially and expanded as it is inserted on the housing 12. The resilience of the material of sleeve 24 biases the sleeve into clamping engagement on the surface 22 0f the housing 12. When using the flash apparatus for remote slave operation using a light source to trigger the light sensitive semi-conductor switch 20, the window is open with the sleeve 24 positioned as shown in FIG. 1. When using the camera and a shutter synchronization cord to trigger the flash, the sleeve 24 is axially positioned over the window to prevent premature triggering of the flash by transient light.

The housing 12 also includes an aperture 26 which receives the shutter sync-cord plug 28 of the circuit module 16 and an aperture 30 in registry with the power supply plug 32 of the circuit module.

The circuit module 16 comprises a circuit mounting member or printed circuit board 34 which is desirably constructed of epoxy glass to provide strength and rigidity for firm support of the input plugs 28 and 32 which receive considerable pressure and abuse when connecting plugs are inserted and removed. The circuit board 34 is also resilient to facilitate assembly of the circuit module 16 in the housing as sub sequently described. The input plug 32 is secured to the board 34 by a retainer ring 33. The semi-conductor switch 20 is supported on a phenolic mounting block 45. The mounting block 45 is anchored to the circuit board 34 by epoxy cement. The leads 37 of the semiconductor switch extend through an aperture 41 in the mounting block 45 and the circuit board 34. The semi-conductor switch 20 and leads 37 are secured to the mounting block 45 and circuit board 34 by silicone cement 43 located in and around the aperture 41. The elastomeric properties of the cement 43 minimize fatigue of the leads 37 due to vibration. The aperture 41 is desirably sufiiciently large to facilitate precise location of the semi-conductor switch 20 on the circuit board 34 to insure registry with the window 18 when the module, 16 is assembled in the housing 12. The mounting block 45 also serves as a spacer to position the semiconductor switch 20 at a point intermediate between the circuit board 34 and the housing 12 to obtain the maximum angle of acceptance.

The circuit module 16 includes a flash tube socket 36 located at the upper end 38 of the circuit board 34. Means are provided to fixedly secure the socket to the end 38 of the circuit board 34. As disclosed, the means are in the form of a radial slot 40 in the socket 36 which receives the upper end 38 of the circuit board- 34. Epoxy cement 39 securely holds the socket to the board 34. A high voltage gas-filled flash tube 42 (FIG. 3) is mounted on a flash tube mounting member or wafer 44. The wafer 44 is provided with current conducting pins 46 which are electrically connected to the terminals of the flash tube.

The circuit module also includes a signal light or neon bulb 48 to indicate recycling and charging of the power supply as hereinafter described in detail. Means are provided for supporting the neon bulb 48 on the socket and in adjacent relation to the flash tube 42.. In the disclosed construction, the means comprises a sleeve or a length of heat shrinkable resilient tubing 50 such as irradiated polyolefin with a meltable interior wall. The upper end 52 of the tubing 50 encapsulates the lower portion of the bulb 48 and the bulb leads. The lower end 54 of the tubing 50 extends through and is in a pressure fit in an aperture 56 in the socket 36. The neon bulb leads can be enclosed with Teflon tubing, or otherwise insulated. As best shown in FIG. 3, the wafer 44 is provided with an aperture 58 to afford withdrawal and replacement of the flash tube 42 over the neon bulb 48. The neon bulb 48 and aperture 58 also serve as a keying arrangement to facilitate location of the pins 46 in the pin apertures 59 in the socket 36.

The flash tube 42 is protected by a transparent cover 62. The cover is desirably constructed of cast Plexiglas or other suitable transparent impact-resistant material with good light transmission-properties. As shown in FIG. 2 the cover 62 includes an upwardly convex dome 64 which can be fabricated independently of the cylindrical wall portion 66 and glued or otherwise secured to the upper end of the wall 66. The lower end of the cover 62is provided with a shoulder or axially extending flange 68 which has a smaller outside diameter than the wall portion 66 and which extends into and frictionally engages the upper end of the housing. When assembled, the shoulder 68 clamps the wafer 44 against the tube socket 36 to minimize accidental displacement and electrical disconnection of the flash tube.

The camera synchronization plug 28 is firmly secured to the circuit board 34 by cement 35 with the terminals projecting through the circuit board as shown in FIG. 4.

When assembling the circuit module 16 in the housing 12, the module is axially inserted in the lower end of the housing and inward pressure is exerted on the plug 28 to clear the margins of the aperture 30 for the power supply plug. The module 16 is adjusted to register the plug 28 with the aperture 26. As shown in FIG. 2, the plug 28 projects into the aperture 26 when the module 16 is assembled, thus preventing angular or axial displacement of the circuit module 16 relative to the housing.

The lower end of the circuit board 34 is anchored by an end cap 72 which has a shoulder 73 extending into the inside of the housing 12.

The end cap 72 includes an outtumed annular flange 74 which seats against the lower end of the housing and a concentric internally and externally threaded bushing 76 threaded into a concentric aperture 78 in the end cap 72. The internal thread is adapted to receive the upstanding threaded stud on a tripod head or a flash gun bracket (not shown). To afford further rigidity to the circuit board 34 and to minimize displacement of the circuit board when installing the power supply cord or camera sync-cord, means are provided on the end cap cooperating with the circuit board for rigidifying the circuit board 34 against translatory displacement.

In the disclosed construction, the means comprises a radial slot 80 located on the inner face 81 of end cap 72 and which receives the lower end 82 of the circuit board 34. The radial slot 80 extends transversely or at right angles to the direction of thrust when inserting the connecting plugs to minimize translatory displacement of circuit board 34. The slot 80 also extends transversely to the longitudinal axis of the circuit connecting members on the plugs 28 and 32.

A notch 84 in the lower end 82 of the circuit board 34 permits extension of the tripod stud (not shown) past the lower margin 86 of the circuit board. The end cap 72 is detachably secured to the lower end of the housing 12 by a plurality of screws 88 which extend through apertures 89 in the housing and are threadably received in threaded radial apertures 90 in end cap 72. When the circuit module 16 is installed, the flash tube 42 is easily inserted in socket 36 and clamped securely against socket 36 by the cover 62. Y

The flash apparatus of the invention also includes a circuit generally designated with the circuit components, connecting leads and printed circuit foil 101 all located on the circuit module 16. The circuit includes the gas-filled flash tube 42 which has an anode 102, a cathode 104 and a trigger electrode 106, and a trigger coil 107 having a primary 108 with first and second terminals, respectively 110 and 112, and a secondary 114 having first and second terminals respectively 1 16 and 118. The circuit includes the power supply input plug 32- which has first, second, third and fourth terminals respectively 120, 122, 124 and 126. Terminals 124 and 126 are connected by a lead 119. The plug 32 is adapted to be connected to a conventional capacitor type power supply 123 with a voltage potential range of 375 to 500 volts. The power input into the circuit 100 from the power supply 123 is determined by the capacitance of the storage capacitor in the power supply and the characteristics of the flash tube.

The input terminals 120, 122, 124 and 126 are respectively connected to terminals 121, 125, 127 and 128 of the power supply 123 by female plug or receptacle 129 which mates with plug 32. The power supply 123 includes a battery 131 having a positive terminal connected to tenninal 121 by a lead 133. The negative terminal of the battery 131 is connected to terminal 128 through a resistor 135. A storage capacitor 137 is connected to terminal 121 by a lead 139 and to terminal 127 by a lead 141. The terminals 122 and make the flash apparatus adapted for use with a camera shutter sync-cord which is connected to a plug or jack (not shown) on the power supply rather than to plug 28 on the circuit module 16.

The circuit 100 includes a resistance bridge having a first resistor having first and second terminals 132 and 134 and a second resistor 136 having first and second terminals 138 and 140. The circuit 100 is provided with a trigger storage capacitor 142 which has a first terminal 144 and a second terminal 146. Current flow through the primary 108 of the trigger coil 107 is initiated by discharge of the trigger storage capacitor 142. Trigger capacitor discharge is controlled by a light activated semigconductor switch or laser 150 which includes an anode 152, a cathode 154 and a gate 156. The semi-conductor switch 150 is made conducting when the flash apparatus is used as a remote slave unit by a light pulse typically provided by another flash unit fired by the camera shutter contacts. Whenthe semi-conductor switch 150 is made conducting by utilizing the camera shutter contacts rather than a light source, the sleeve 24 is located over the window 18 to prevent premature triggering of the circuit by transient light. The semi-conductor switch 150 is protected by a zener diode having a cathode 174 and an anode 176.

The circuit also includes a third resistor 160 having a first terminal 162 and a second terminal 164, a fourth resistor 166 having a first terminal 168 and a second terminal 170, and a fifth resistor 131A which is connected to the terminal 122 and to the gate 156 by a lead 196.

The anode 102 of flash tube 42, the first terminal 132 of resistor 130 and the first terminal 162 of resistor 160 are connected to input terminal 120 by a lead 182. The terminal 164 of resistor 160 is connected to terminal 180 of plug 28. The resistor 160 and the zener diode 172 provide gate circuit protection for the switch 150. The resistor 160 also provides isolation of plug 28 and thus the camera from the positive side of the power source. The fifth resistor 131 also cooperates with the zener diode 150 to provide gate circuit protection. The other terminal 184 of plug 28 is connected to the gate 156 by the lead 196.

One terminal 188 of the signal lamp or neon ready light 50 is connected to the terminal 138 of the second resistor 136, the second terminal 134 of resistor 130, the first terminal 144 of capacitor 142, and the terminal 110 of the primary 108 of trigger coil 106 by a lead 190. The other terminal 192 of the signal light 50 is connected to the input terminal 126 and the second terminal 140 of second resistor 136, the second terminal 146 of the capacitor 142, the anode 176 of zener diode 172, the second terminal 170 of resistor 166, the cathode 154 of semi-conductor switch 150 and the cathode 104 of flash tube 42 by a lead 194. The cathode 174 of zener diode 172 and the first terminal 168 of the fourth resistor 166 are connected to the gate 156 of the semi-conductor switch 150 by the lead 196. The terminal 112 of the primary of trigger coil 107 and the terminal 118 of the secondary 114 are connected to the anode 152 of semi-conductor switch 150 by a lead 198.

An embodiment of the invention was successfully operated with the components having the following values: a first resistor 130 having a resistance of 3.9 megohms; a second resistor 136 having a resistance of 2.2 megohms; a third resistor 160 having a resistance of megohms; a capacitor 142 having a capacitance of 0.5 mfd and a 200 volt rating; a zener diode 172 with a 6.2 volt avalanche rating; a fourth resistor 166 having a resistance of 56,000 ohms; and a fifth resistor 131A having a resistance of 10 megohms; a trigger coil having a primary to secondary ratio of 1:50; with the semi-conductor switch 150 being a GE. Laser L9-B; and the flash tube 42 a Kemlite DW-2.

The neon light 50 is connected to the circuit to form a relaxation oscillator with the oscillation time constant determined by the resistance of the resistor 136 and the capacitance of the capacitor 142. With the disclosed circuit values, the interval between flashes of the signal light 50 is approximately 1 second. The signal light 50 commences to pulsate when the predetermined charge level of 160-175 volts is attained on the trigger storage capacitor 142. The location of the ready light in the transparent cover and the pulsating character of the signal light make the signal light visible from any angle and at substantial distances.

To minimize idling battery drain of the power supply, the resistors 130 and 136 of the resistance bridge each have a resistance of over 2 megohms. The ratio of the resistances between resistor 130 and 136 is critical to maintain the stability of the semi-conductor switch 150 and prevent intermittent pre-ignition. A range of ratios of not greater than 2:1 and not less than 5:3 between resistor and resistor 136 is essential to maintain stability of the laser. This range of ratios was emperically determined and permits the use of a 3.9 megohm resistance for resistor 130 and a 2.2 megohm resistance for resistor 136 with the resistors having a tolerance of 5 percent. Thus, 3.9 megohms plus 5 percent or 0.195 megohms will give a value of 4.095 megohms and 2.2 megohms less 5 percent or 0.110 megohms gives a resistance value of 2.090 or a ratio of 2: 1. The ratio of 5:3 is determined by subtracting 5 percent or 0.195 megohms from 3.9 megohms to achieve a resistance value of 3.705 for resistor 130 and the addition of 0.110 or 5 percent of 2.2 megohms to 2.2 megohms gives a value of 2.3 10 megohms and a ratio of approximately 5:3.

When the semi-conductor switch is made conducting, either by use of camera shutter contacts or with a light pulse, the capacitor 142 discharges through the primary 108 of trigger coil 107 which thus causes a pulse in the secondary 114 and a potential on the trigger electrode of 9,000 to 10,000 volts to lower the ionization threshold of the gas in the tube and cause a discharge of the storage capacitor 137 in the power supply.

What is claimed is:

1. Flash apparatus comprising a tubular housing having a hollow interior, a window in said housing, a semi-conductor switch having a light sensitive gate and supported within said housing and in registry with said window, semi-rigid means on the outside surface of said housing and freely slideable on said housing for selectively opening and closing said window, a circuit assembly including circuit elements receivable in said housing, said flash apparatus being alternatively operable to afford a slave operated mode with said semi-rigid means remote from said window and exposing said semi-rigid conductor switch for light actuation of said semiconductor switch and a camera shutter operated mode for said gate of said semiconductor switch with said semi-rigid means closing said window, said circuit elements including a flash tube having an anode, cathode, and trigger electrode, a trigger capacitor, a trigger coil having a primary and secondary, a storage capacitor, an input jack adapted to be connected to the shutter contacts of a camera, and circuit means electrically connecting said circuit elements and said semi-conductor switch to cause a discharge of said trigger capacitor through said trigger coil to cause a potential on said trigger electrode and cause discharge of said storage capacitor to illuminate said flash tube by one of completing a circuit through said input jack to said gate and exposing said gate to a light source.

2. Apparatus in accordance with claim 1 wherein said means for selectively opening and closing said window comprises a sleeve in frictional engagement with the outside surface of said housing.

3. Apparatus in accordance with claim 2 wherein said sleeve has an axial slot extending the length of said sleeve to afford expansion of said sleeve for assembly on said housing in a stressed condition to bias said sleeve against said housing to retain said sleeve at a selected position.

4. Flash apparatus comprising a tubular housing, a circuit assembly receivable in said housing, said assembly including a circuit mounting member, a flash tube socket fixedly secured to one end of said mounting member and extending longitudinally of said mounting member, a flash tube, a flash tube supporting member connected to said flash tube and having a plurality of current conducting pins receivable in said socket, an end cap having an end cap portion receivable in said housing, and means on said end cap cooperating with said circuit mounting member for rigidifying said circuit mounting member against translatory displacement.

'5. Apparatus in accordance with claim 4 including an aperture in said housing, an input plug secured to said circuit mounting member, said input plug including circuit connecting members interfitting in said aperture to prevent axial and angular displacement of said circuit mounting member, and wherein said circuit mounting member is resilient to afford insertion and removal of said plug from said aperture and insertion and withdrawal of said mounting member into and from said housing.

6. Apparatus in accordance with claim 4 wherein said circuit assembly includes a signal light, means for supporting said signal light in axially extending relationship on said socket and an aperture in said flash tube supporting member for receiving said signal light and affording axial withdrawal of said flash tube mounting member over said signal light.

7. Apparatus in accordance with claim 6 wherein said means for mounting said signal light on said socket comprises a resilient sleeve encapsulating the lower end of said signal light, said sleeve extending into and being anchored in said socket.

8. Apparatus in accordance with claim 4 including a transparent cover for said flash tube, said cover having a cover portion which extends into said tubular housing and engages said flash tube supporting member to clamp said flash tube supporting member against said socket.

9. Apparatus in accordance with claim wherein said means on said end cap cooperating with said circuit mounting member comprises a radially extending inwardly open slot on an inner face of said end cap, said slot receiving one end of said circuit mounting member and extending transversely to the longitudinal axis of circuit connecting members on said plug.

10. Apparatus in accordance with claim 9 including an internally threaded concentric bushing in said end cap and a notch in said circuit mounting member in registry with said bushing, said notch being adapted to receive the upper end of the threaded stud of a flash gun supporting device when the stud is threaded in said bushing.

11. Flash apparatus comprising a tubular housing, a circuit board having electrically conducting paths on said board, circuit components mounted on said board, a flash tube socket having electrical connectors and having a radial slot which receives one end of said circuit board, means for securing said circuit board to said socket, a flash tube, a flash tube mounting member connected to said flash tube and having pins adapted to project into and electrically connect with said connectors in said socket, said circuit board being adapted to be inserted in said housing, an end cap having .a radial slot adapted to receive the other end of said'circuit board, said radial slot in said end cap preventing axial, angular and translatory movement of said circuit board, said end cap having an annular shoulder which interfits in said other end of said tubular housing, an aperture in said housing, a connector plug mounted on said circuit board and adapted to interfit in said aperture in said housing to prevent axial and angular movement of said circuit board, and a transparent cover for said flash tube, said cover having a shoulder which interfits in said other end of said housing and extends inwardly in said housing to clamp said flash tube mounting member against said socket.

12. A flash circuit comprising a flash tube having a cathode, anode and triggering electrode, a light sensitive semi-conductor switch having a cathode, anode and gate, and a high impedance state and low impedance state, a trigger coil having a primary and secondary, said primary and secondary each having first and second terminals, a trigger storage capacitor having first and second terminals, first, second and third input terminals, a resistance bridge comprising first and second resistors, each resistor having first and second terminals, said first terminal of said second resistor being connected to said I second terminal of said first resistor, circuit means connecting said first input terminal to said first terminal of said first resistor and said anode of said flash tube, circuit means connecting said first terminal of said trigger storage capacitor and said first terminal of said primary of said trigger coil, circuit means connecting said third input terminal to said second terminal of said second resistor, to said second terminal of said trigger capacitor, said cathode of said semi-conductor switch, and to said cathode of said flash tube, circuit means connecting said first terminal of said secondary of said trigger coil to said trigger electrode of said flash tube, circuit means connecting said second terminals of said primary and said secondary to said anode of said semi-conductor switch, an input plug adapted to be connected to the flash synchronization contacts of a camera shutter, said input plug having first and second terminals, a third resistor having first and second terminals, said first terminal of said third resistor being connected to said first input terminal and circuit means connecting said first terminal of said input plug to said second temiinal of said third resistor, circuit means connecting said second terminal of said input plug to said gate of said semi-conductor switch, a power supply having a storage capacitor with terminals connectable to said first and third input terminals, including a neon signal light having first and second terminals with means electrically connecting said first terminal of said signal light to said first terminal of said second resistor and means electrically connecting said second terminal of said neon light to said third input terminal so that said neon light is in parallel connection with said trigger storage capacitor, said second resistor and said semi-conductor switch to form a relaxation oscillator to cause said neon light to commence flashing at a constant, visible and perceptible interval when said trigger capacitor repetitively attains a pre-determined charge sufiicient for ionizing said neon bulb and said trigger capacitor repetitively discharges through said second resistor and said semi-conductor switch when said switch is in said high impedance state.

13. A flash circuit in accordance with claim 12 including a zener diode having an anode and cathode, said cathode being electrically connected to said gate and said anode being electrically connected to said cathode of said semi-conductor switch, a fourth resistor having first and second terminals, said first terminal being electrically connected to said gate and said second terminal being electrically connected to said cathode of said semi-conductor switch, and a fifth resistor connected between said second input terrm'nal and said gate of said semiconductor switch.

14. A flash circuit in accordance with claim 12 wherein each of said resistors in said resistance bridge has a resistance greater than 2 megohms and the ratio of the resistance of said first resistor to the resistance of said second resistor is no greaterthan 2:1 and nolessthan 5:3.

15. A flash circuit in accordance with claim 14 wherein said first resistor has a resistance of 3.9 megohms and said second resistor has a resistance of 2.2 megohms.

16. Flash apparatus including a housing, a flash tube having an anode, a cathode and a trigger electrode, a flash tube socket connected to said housing at one end of said'housing, a flash tube supporting member connected to said socket, a transparent cover for said flash tube, a neon signal light supported on said socket within said cover and adjacent to said flash tube in an axially extending relationship on said socket, a circuit including a storage capacitor connected in parallel with said flash tube, said circuit further including a semi-conductor switch having an anode, cathode and gate, a trigger coil having a primary connected to said anode of said semi-conductor switch and a secondary connected to said trigger electrode of said flash tube, a trigger storage capacitor connected to said primary and said gate of said switch, and first and second resistors forming a resistance bridge, connected in parallel with said flash tube and in parallel with said storage capacitor, said neon signal light being connected in parallel with said trigger capacitor, said second resistor and said semi-conductor switch to form a relaxation oscillator for monitoring the condition of said storage capacitor, said semi-conductor switch and said trigger capacitor and causing visible perceptible flashes of said signal light at constant intervals when said trigger capacitor repetitively charges and discharges through said second resistor and said semi-conductor switch as said trigger capacitor attains a pre-deterrnined charge.

17. A flash circuit comprising a flash tube having a trigger electrode, a light sensitive semi-conductor switch, a trigger storage capacitor, a trigger coil having a primary connected to said trigger capacitor and a secondary connected to said trigger electrode and said primary connected to said semi-consecond resistor, said trigger capacitor and said semi-conductor switch so that said second resistor, said trigger storage capacitor and said semi-conductor switch form a relaxation oscillator to cause flashing of said signal light at a constant perceptible interval when said trigger capacitor repetitively charges and discharges through said second resistor and said semi-conductor switch. 

1. Flash apparatus comprising a tubular housing having a hollow interior, a window in said housing, a semi-conductor switch having a light sensitive gate and supported within said housing and in registry with said window, semi-rigid means on the outside surface of said housing and freely slideable on said housing for selectively opening and closing said window, a circuit assembly including circuit elements receivable in said housing, said flash apparatus being alternatively operable to afford a slave operated mode with said semi-rigid means remote from said window and exposing said semi-rigid conductor switch for light actuation of said semi-conductor switch and a camera shutter operated mode for said gate of said semi-conductor switch with said semi-rigid means closing said window, said circuit elements including a flash tube having an anode, cathode, and trigger electrode, a trigger capacitor, a trigger coil having a primary and secondary, a storage capacitor, an input jack adapted to be connected to the shutter contacts of a camera, and circuit means electrically connecting said circuit elements and said semi-conductor switch to cause a discharge of said trigger capacitor through said trigger coil to cause a potential on said trigger electrode and cause discharge of said storage capacitor to illuminate said flash tube by one of completing a circuit through said input jack to said gate and exposing said gate to a light source.
 2. Apparatus in accordance with claim 1 wherein said means for selectively opening and closing said window comprises a sleeve in frictional engagement with the outside surface of said housing.
 3. Apparatus in accordance with claim 2 wherein said sleeve has an axial slot extending the length of said sleeve to afford expansion of said sleeve for assembly on said housing in a stressed condition to bias said sleeve against said housing to retain said sleeve at a selected position.
 4. Flash apparatus comprising a tubular housing, a circuit assembly receivable in said housing, said assembly including a circuit mounting member, a flash tube socket fixedly secured to one end of said mounting member and extending longitudinally of said mounting member, a flash tube, a flash tube supporting member connected to said flash tube and having a plurality of current conducting pins receivable in said socket, an end cap having an end cap portion receivable in said housing, and means on said end cap cooperating with said circuit mounting member for rigidifying said circuit mounting member against translatory displacement.
 5. Apparatus in accordance with claim 4 including an aperture in said housing, an input plug secured to said circuit mounting member, said input plug including circuit connecting members interfitting in said aperture to prevent axial and angular displacement of said circuit mounting member, and wherein said circuit mounting member is resilient to afford insertion and removal of said plug from said aperture and insertion and withdrawal of said mounting member into and from said housing.
 6. Apparatus in accordance with claim 4 wherein said circuit assembly includes a signal light, means for supporting said signal light in axially extending relationship on said socket and an aperture in said flash tube supporting member for receiving said signal light and affording axial withdrawal of said flash tube mounting member over said signal light.
 7. Apparatus in accordance with claim 6 wherein said means for mounting said signal light on said socket comprises a resilient sleeve encapsulating the lower end of said signal light, said sleeve extending into and being anchOred in said socket.
 8. Apparatus in accordance with claim 4 including a transparent cover for said flash tube, said cover having a cover portion which extends into said tubular housing and engages said flash tube supporting member to clamp said flash tube supporting member against said socket.
 9. Apparatus in accordance with claim 5 wherein said means on said end cap cooperating with said circuit mounting member comprises a radially extending inwardly open slot on an inner face of said end cap, said slot receiving one end of said circuit mounting member and extending transversely to the longitudinal axis of circuit connecting members on said plug.
 10. Apparatus in accordance with claim 9 including an internally threaded concentric bushing in said end cap and a notch in said circuit mounting member in registry with said bushing, said notch being adapted to receive the upper end of the threaded stud of a flash gun supporting device when the stud is threaded in said bushing.
 11. Flash apparatus comprising a tubular housing, a circuit board having electrically conducting paths on said board, circuit components mounted on said board, a flash tube socket having electrical connectors and having a radial slot which receives one end of said circuit board, means for securing said circuit board to said socket, a flash tube, a flash tube mounting member connected to said flash tube and having pins adapted to project into and electrically connect with said connectors in said socket, said circuit board being adapted to be inserted in said housing, an end cap having a radial slot adapted to receive the other end of said circuit board, said radial slot in said end cap preventing axial, angular and translatory movement of said circuit board, said end cap having an annular shoulder which interfits in said other end of said tubular housing, an aperture in said housing, a connector plug mounted on said circuit board and adapted to interfit in said aperture in said housing to prevent axial and angular movement of said circuit board, and a transparent cover for said flash tube, said cover having a shoulder which interfits in said other end of said housing and extends inwardly in said housing to clamp said flash tube mounting member against said socket.
 12. A flash circuit comprising a flash tube having a cathode, anode and triggering electrode, a light sensitive semi-conductor switch having a cathode, anode and gate, and a high impedance state and low impedance state, a trigger coil having a primary and secondary, said primary and secondary each having first and second terminals, a trigger storage capacitor having first and second terminals, first, second and third input terminals, a resistance bridge comprising first and second resistors, each resistor having first and second terminals, said first terminal of said second resistor being connected to said second terminal of said first resistor, circuit means connecting said first input terminal to said first terminal of said first resistor and said anode of said flash tube, circuit means connecting said first terminal of said trigger storage capacitor and said first terminal of said primary of said trigger coil, circuit means connecting said third input terminal to said second terminal of said second resistor, to said second terminal of said trigger capacitor, said cathode of said semi-conductor switch, and to said cathode of said flash tube, circuit means connecting said first terminal of said secondary of said trigger coil to said trigger electrode of said flash tube, circuit means connecting said second terminals of said primary and said secondary to said anode of said semi-conductor switch, an input plug adapted to be connected to the flash synchronization contacts of a camera shutter, said input plug having first and second terminals, a third resistor having first and second terminals, said first terminal of said third resistor being connected to said first input terminal and circuit means connecting said first terminal of said input plug to said second terminal of said third resistor, circuit means connecting said second terminal of said input plug to said gate of said semi-conductor switch, a power supply having a storage capacitor with terminals connectable to said first and third input terminals, including a neon signal light having first and second terminals with means electrically connecting said first terminal of said signal light to said first terminal of said second resistor and means electrically connecting said second terminal of said neon light to said third input terminal so that said neon light is in parallel connection with said trigger storage capacitor, said second resistor and said semi-conductor switch to form a relaxation oscillator to cause said neon light to commence flashing at a constant, visible and perceptible interval when said trigger capacitor repetitively attains a pre-determined charge sufficient for ionizing said neon bulb and said trigger capacitor repetitively discharges through said second resistor and said semi-conductor switch when said switch is in said high impedance state.
 13. A flash circuit in accordance with claim 12 including a zener diode having an anode and cathode, said cathode being electrically connected to said gate and said anode being electrically connected to said cathode of said semi-conductor switch, a fourth resistor having first and second terminals, said first terminal being electrically connected to said gate and said second terminal being electrically connected to said cathode of said semi-conductor switch, and a fifth resistor connected between said second input terminal and said gate of said semi-conductor switch.
 14. A flash circuit in accordance with claim 12 wherein each of said resistors in said resistance bridge has a resistance greater than 2 megohms and the ratio of the resistance of said first resistor to the resistance of said second resistor is no greater than 2:1 and no less than 5:3.
 15. A flash circuit in accordance with claim 14 wherein said first resistor has a resistance of 3.9 megohms and said second resistor has a resistance of 2.2 megohms.
 16. Flash apparatus including a housing, a flash tube having an anode, a cathode and a trigger electrode, a flash tube socket connected to said housing at one end of said housing, a flash tube supporting member connected to said socket, a transparent cover for said flash tube, a neon signal light supported on said socket within said cover and adjacent to said flash tube in an axially extending relationship on said socket, a circuit including a storage capacitor connected in parallel with said flash tube, said circuit further including a semi-conductor switch having an anode, cathode and gate, a trigger coil having a primary connected to said anode of said semi-conductor switch and a secondary connected to said trigger electrode of said flash tube, a trigger storage capacitor connected to said primary and said gate of said switch, and first and second resistors forming a resistance bridge, connected in parallel with said flash tube and in parallel with said storage capacitor, said neon signal light being connected in parallel with said trigger capacitor, said second resistor and said semi-conductor switch to form a relaxation oscillator for monitoring the condition of said storage capacitor, said semi-conductor switch and said trigger capacitor and causing visible perceptible flashes of said signal light at constant intervals when said trigger capacitor repetitively charges and discharges through said second resistor and said semi-conductor switch as said trigger capacitor attains a pre-determined charge.
 17. A flash circuit comprising a flash tube having a trigger electrode, a light sensitive semi-conductor switch, a trigger storage capacitor, a trigger coil having a primary connected to said trigger capacitor and a secondary connected to said trigger electrode and said primary connected to said semi-conductor switch to afford a circuit flow through said primary to cause an impulse in said secondary to fire said flash tube when said semi-conductor switch is made conducting, a resistance bridge having first and second resistors, a neon signal light for monitoring the condition of said trigger capacitor and said semi-conductor switch and circuit means connecting said trigger capacitor and said resistance bridge to a main storage capacitor and connecting said resistance bridge to said flash tube and connecting said neon light in parallel with said second resistor, said trigger capacitor and said semi-conductor switch so that said second resistor, said trigger storage capacitor and said semi-conductor switch form a relaxation oscillator to cause flashing of said signal light at a constant perceptible interval when said trigger capacitor repetitively charges and discharges through said second resistor and said semi-conductor switch. 